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EWRB Theory Exam Prep Questions with Complete Solutions
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EWRB Theory Exam Prep Questions with Complete Solutions
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EWRB Theory Exam Prep Questions withComplete Solutions
What is the minimum value of the permitted test result for the insulation resistance
test of a three-phase, 400V, mains cable? - ANSWER 1MΩ
What is the maximum value of the permitted test result for an earth leakage test of
a 230V, Class 1, plug-in appliance? - ANSWER 5mA
State TWO types of fault that a MCB provides protection for. - ANSWER - Short-
Circuit - Overload
What type of fault does a RCD provide protection for? - ANSWER Earth Faults
State the full name for a PRCD. - ANSWER Portable Residual Current Device.
State the full name for a RCBO. - ANSWER Residual Circuit Breaker with
Overcurrent protection.
State the full name for a SRCD. - ANSWER Socket Residual Circuit Breaker.
State ONE practical method used to reduce iron losses in the construction of
a transformer. - ANSWER ANY ONE:
- Laminate the iron core.
- Use special types of alloy for the core.
, State TWO methods of reducing the stroboscopic effect of a fluorescent fittings
installed across three-phases. - ANSWER ANY TWO:
- Connect fittings on different phases.
- In double-tube fittings, connect a capacitor in series with one ballast or install
lead/lag fittings.
- Intersperse incandescent lighting with the fluorescent lighting.
Explain the term SENSITIVITY as it applies to a RCD. - ANSWER Sensitivity is the
current imbalance (earth leakage) required to trip the RCD.
In a Star connected electrical system, state the angle between line voltage and
phase voltage. - ANSWER 30º
In New Zealand, what type of RCD is required to be voltage dependent? - ANSWER
Portable Residual Current Device (PRCD)
State the maximum residual current rating for a RCD installed in a patient treatment are.
- ANSWER 10mA
State TWO reasons why a RUN CAPACITOR would be fitted to a single-phase,
split-phase induction motor. - ANSWER ANY TWO:
- Quieter running.
- Better running torque.
- Less current draw.
- Increased efficiency.
Name TWO components that are typically used to smooth the DC output of a rectifier. -
ANSWER ANY TWO:
- Capacitors
- Inductors
- Resistors
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